The subject matter described herein relates generally to wind turbines and, more particularly, to a method of controlling an electric power output of at least one wind turbine and/or a wind turbine farm.
Generally, a wind turbine includes a rotor that includes a rotatable hub assembly having multiple blades. The blades transform wind energy into a mechanical rotational torque that drives one or more generators via the rotor. The generators are sometimes, but not always, rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the rotor for the generator to efficiently convert the rotational mechanical energy to electrical energy, which is fed into a utility grid via at least one electrical connection. Gearless direct drive wind turbines also exist. The rotor, generator, gearbox and other components are typically mounted within a housing, or nacelle, that is positioned on a base that includes a truss or tubular tower for example. At least some of the known wind turbines are physically nested together in a common geographical region to form a wind turbine farm. Such known wind turbine farms are typically electrically connected to an electrical grid.
Many known electrical grids have voltage tolerance ranges and require power factor tolerance ranges that facilitate reliable electric power transmission and distribution over a wide variety of operational conditions to serve a broad market. For example, many known electrical grids include a grid voltage tolerance range that extends from 90% of nominally rated voltage to 110% of nominally rated voltage. Also, for example, a typical electrical grid power factor tolerance range for generation equipment extends from a +0.9 power factor (pf) to a −0.9 pf. These operational tolerance ranges define the electrical parameters for all components connected to the grid including electric current rating and power draw at voltages in the lowest end of the voltage range and voltages at the highest end of the voltage range. Similarly, in at least some known wind turbine farms, each wind turbine has design, or nameplate parameters, that include power generation, current, voltage, and power factor tolerance ranges. Therefore, many known wind turbines are designed to operate within a voltage and power factor window that is complimentary to the associated electrical grid. However, during operation of such known wind turbines in such known electrical grids, to accommodate potential large voltage transients in the grid, wind turbines are operated below upper power and current parameters with sufficient margin to those upper parameters to tolerate such large grid-induced voltage transients in any direction. Therefore, electric power generation opportunities may not be realized by the known wind farms and other power generators connected to the grid may provide the electric power, thereby decreasing the operating effectiveness and efficiency of the wind farms and possibly incurring a lost economic opportunity for the owners/operators of the wind farms.